Roughly chop tempeh and mushrooms. Place in food processor, add walnuts, and pulse gently multiple times until everything is evenly chopped and resembles texture of ground beef, being careful not to overprocess (or it will be too mushy). Pulse in soy sauce or tamari, tomato paste, oregano, cumin, paprika, garlic powder, onion powder, and salt.

In skillet, heat oil over medium heat. Add processed ingredients and cook for 7 to 10 minutes, stirring occasionally, until mixture darkens and has lost some of its moisture. Stir in vinegar and heat for 1 minute.

To make salsa, in bowl, toss together avocado, tomatoes, onion, jalapeno, cilantro, salt, and lime juice.

To serve, top tortillas with walnut mixture and salsa.